Pages

Record-High Antarctic Sea Ice Levels Don't Disprove Global Warming

The region's ice has weathered global warming better than Arctic ice

Steve Goddard must be feeling shell shocked. Only a few months ago at the winters peak, the Arctic Sea Ice extent (not volume) was almost normal which he touted loudly on his blog, only to see the fastest melt on record to a new low. With the Battle lost he turns his attention to the Antarctic winter and the growing ice there.

Distracting from the news that Arctic sea-ice extent reached a record
low on Sept. 16 is a widely circulating blog article claiming that at
the opposite end of the Earth, Antarctic sea ice is more than making up
for the losses.

In the post,
climate change skeptic and blogger Steven Goddard states that Antarctic
sea ice reached its highest level ever recorded for the 256th day of
the calendar year on Sept. 12. He reasons that the Southern Hemisphere
must be balancing the warming of the Northern Hemisphere by becoming
colder (and thus, net global warming is zero).

Despite its lack of scientific support, Goddard's post has garnered
attention around the Web. In a Forbes.com column about the record high
Antarctic sea ice,
skeptic James Taylor writes, "Please, nobody tell the mainstream media
or they might have to retract some stories and admit they are
misrepresenting scientific data."

But if anyone had asked an actual scientist, they would have learned
that a good year for sea ice in the Antarctic in no way nullifies the
precipitous drop in Arctic sea-ice levels year after year - or the
mounds of other evidence indicating global warming is really happening.

"Antarctic sea ice hasn't seen these big reductions we've seen in the
Arctic. This is not a surprise to us," said climate scientist Mark
Serreze, director of the NSIDC. "Some of the skeptics say 'Well,
everything is OK because the big changes in the Arctic are essentially
balanced by what's happening in the Antarctic.' This is simply not
true." [Former Global Warming Skeptic Makes a 'Total Turnaround']

Projections made from climate models all predict that global warming
should impact Arctic sea ice first and most intensely, Serreze said. "We
have known for many years that as the Earth started to warm up, the
effects would be seen first in the Arctic and not the Antarctic. The
physical geography of the two hemispheres is very different. Largely as a
result of that, they behave very differently."

The Arctic, an ocean surrounded by land, responds much more directly to
changes in air and sea-surface temperatures than Antarctica, Serreze
explained. The climate of Antarctica, land surrounded by ocean, is
governed much more by wind and ocean currents. Some studies indicate
climate change has strengthened westerly winds in the Southern
Hemisphere, and because wind has a cooling effect,
scientists say this partly accounts for the marginal increase in sea
ice levels that have been observed in the Antarctic in recent decades.

"Another reason why the sea-ice extent in the Antarctic is remaining fairly high is, interestingly, the ozone hole,"
Serreze told Life's Little Mysteries. This hole was carved out over
time by chlorofluorocarbons, toxic chemicals formerly that were used in
air conditioners and solvents before being banned. "The ozone hole
affects the circulation of the atmosphere down there. Because of the
ozone hole, the stratosphere above Antarctica is quite cold. Ozone in
the stratosphere absorbs UV light, and less absorption [by] ozone makes
the stratosphere really cold. This cold air propagates down to the
surface by influencing the atmospheric circulation in the Antarctic, and
that keeps the sea ice extensive."

But these effects are very small, and Antarctic sea-ice levels have
increased only marginally. In the coming decades, climate models suggest
rising global temperatures will overwhelm the other influences and
cause Antarctic sea ice to scale back, too.

The extent of Arctic sea ice at its summertime low point has dropped 40
percent in the past three decades. The idea that a tiny Antarctic ice
expansion makes up for this - that heat is merely shifting from the the
Southern Hemisphere to the Northern and therefore global warming must
not be happening - is "just nonsense," Serreze said.